A CMOS ANALOG INTEGRATED CIRCUIT FOR PIXEL X-RAY DETECTOR

A front-end read-out application specific integrated circuit (ASIC) for a multichannel pixel X-Ray detector system has been fabricated and tested. The chip provides signal amplification for pixelated compound semiconductors such as Cadmium Telluride ( CdTe ) and Cadmium Zinc Telluride ( CZT ) with either 1 mm or 200 μm pitch. Both the detector (compound semiconductor) and ASIC are combined to target future research applicable to spectroscopic imaging in high intensity X-Ray biomedical detector systems. The ASIC was fabricated in a 0.35 μm process by Austria Microsystems and consists of 32 channels, where each channel contains a charge-sensitive amplifier, a pulse shaper and two further stages of amplification providing an overall gain of 1 mV per kilo electron volt (keV) for photons within the energy range of 30–120 keV. The preamplifier and shaper circuits are designed for both positive and negative charge collection (electrons and holes) produced by the CdTe or CZT detectors. The ASIC's shaper has been designed with a time constant of 100 ns to allow operation at photon rate events above 1 Million photons per pixel per second. The design and characterization of the readout chip will be discussed in this paper presenting results from both the simulated and the fabricated chip.